This application generally to an arrangement for a power drive train, and more specifically to an arrangement and connection of an engine to a transmission, and even more particularly to an arrangement of a rear or mid-mounted engine, transfer case, and transmission having application in a land transport vehicle, and to an arrangement and connection of an engine and transmission to a propulsion shaft in a marine vehicle such as a boat.
Conventionally, heavy-duty transporter vehicles such as used in buses, tractor-trailer rigs, towing, dump trucks, garbage trucks, concrete mixing trucks, fire trucks, and recreational vehicles, for example, require large, heavy propulsion equipment. Such equipment includes, for example, gasoline or diesel engines and transmissions, and other drive train components such as transfer cases and differentials connecting to driven axles and wheels.
Further, boat and ship propulsion equipment can also be large and heavy, and can have an adverse impact on the trim and stability of the vessel, depending on the location of the propulsion equipment, e.g., diesel engine, reduction gear, and propulsion shaft and thrust bearings, with respect to the center of gravity and center of buoyancy of the vessel.
In the case of a tractor used for hauling a trailer, a front-mounted diesel engine is generally used, with the driver's cab situated above the engine. This arrangement results in several undesirable characteristics, including the cab being located high above the ground and almost directly over the engine, causing difficulty in entry, and the presence of high noise and vibration levels which can lead to driver fatigue and discomfort. A rear or mid-engine mounted engine arrangement could overcome or reduce the problems associated with the high cab, and could also reduce the noise and vibrations experienced by persons riding in the cab.
In many rear-mounted engine applications, conventional wisdom in the automotive propulsion field dictates that a minimum distance of approximately 120 inches or 3 meters is needed from the driven rear axle to the back of the engine. This distance is required to provide for essentially straight line interconnection of the drive components, i.e., a rearward facing engine, transmission, and drive shaft to a rear differential connected to the rear driven axle. This places a large weight located along a relatively long moment arm behind the rear driven axle, which essentially acts as a fulcrum. This resulting relatively large moment tends to make the front end of the vehicle rotationally rise up about the rear axle when a bump in the road is encountered, for example. To counter the tendency for the front end to lift, an optional undriven, so-called “tag axle” is often placed behind the driven axle to counter the action of the large moment, and thus prevent the front end from lifting off the road. The use of tag axles is common in buses, and dump trucks, for example.
In the case of buses used for intra-city transport, the engine is often transversely mounted in the rear of the vehicle, using a so-called “V-drive” arrangement. This arrangement can reduce the moment arm discussed above, however, due to practical considerations, this type of transverse engine drive arrangement is generally limited to engines having a horsepower rating of 250 HP or less, and may not provide the needed power for heavy-duty applications.
What is needed then is a drive arrangement for a transport vehicle which overcomes the above-noted problems, while providing the ability to use a relatively high powered and heavier engine and transmission. What is further needed is an engine drive arrangement which allows a reduction in the cab height of a transport vehicle such as a tractor, and which also reduces the undesirable noise and vibration imparted to the cab. What is still further needed is an engine drive arrangement which places a rear-mounted engine and transmission near the driven axle to reduce the moment arm and moment, and which reduces the tendency for the front end of the transport vehicle to rise from the roadway. What is even still further needed is an engine drive arrangement which places a rear-mounted engine and transmission near the driven axle in such a manner that, in certain applications, the need for a tag axle may be eliminated.